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Ivo Wolf

Publications and source records attributed to Ivo Wolf.

8 recordsLinked to original sources
PubMed2006

A clinical study of annular geometry and dynamics in patients with ischemic mitral regurgitation: new insights into asymmetrical ring annuloplasty.

OBJECTIVE: Recent studies in animals showed that regional annulus distortion is a major determinant of ischemic mitral regurgitation (IMR) and accordingly suggested new surgical approaches with asymmetrical annuloplasty rings. As accurate measurement of annulus in patients is still a challenge, we performed this study to analyze the changes in three-dimensional annular geometry in patients with IMR compared to primary valvular lesions. METHODS: We studied 110 patients divided into three groups: (1) 30 with coronary artery disease without IMR, (2) 38 with chronic IMR, and (3) 42 with MR due to primary valvular lesions. Longitudinal and septal-lateral annulus diameters; global diastolic and systolic annular area and its percentual shortening, diastolic and systolic areas of six regions corresponding to the segmental Carpentier classification were measured by 3D-echocardiography. The degree of MR was assessed by three-dimensional color Doppler. Global and regional left ventricular geometry were assessed by sphericity index and by measuring anterior and posterior tethering of papillary muscles. RESULTS: Patients with significant IMR (group 2) showed larger longitudinal (52.7+/-3.9 mm vs 41.8+/-2.9 mm; p<0.01) and antero-lateral (31.8+/-3.5mm vs 26.7+/-2.8mm; p<0.01) annular diameters than the patients with MR due to primary valvular lesions (group 3). Diastolic (997.8+/-64.9 mm(2) vs 700.7+/-46.8mm(2); p<0.01) and systolic (894.9+/-57.3mm(2) vs 547.3+/-35.0mm(2); p<0.01) annular areas were larger in group 2 than in group 3. Annular area change was significantly lower in the group with ischemic mitral regurgitation than in the group with primary valvular lesions (10.3+/-1.1% vs 21.9+/-1.6%; p<0.01). Regional annular areas of the six sectors were homogeneously larger in group 2 than in group 3. The sector P3 did not show larger area than the other ones. The degree of MR, as assessed by the volumes of regurgitant jets, was higher in the group with primary valvular lesions than in the patients with IMR (32.6+/-13.4 cm(3) vs 23.1+/-11.1cm(3); p<0.01). CONCLUSIONS: This study showed that annular enlargement in patients with IMR affects the different annular regions to the same extent. An ideal surgical repair of IMR should be individually tailored after quantitative assessment measurement of geometry and function of each single component of the mitral valve complex.

Aged↗
PubMed2006

Effect of 3D ultrasound probes on the accuracy of electromagnetic tracking systems.

In the last few years, 3D ultrasound probes have became readily available. New fields of image-guided surgery applications are opened by attaching small electromagnetic position sensors to 3D ultrasound probes. However, nothing is known about the distortions caused by 3D ultrasound probes regarding electromagnetic sensors. Several trials were performed to investigate error-proneness of state-of-the-art electromagnetic tracking systems when used in combination with 3D ultrasound probes. It was found that 3D ultrasound probes do distort electromagnetic sensors more than 2D probes do. When attaching electromagnetic sensors to 3D probes, maximum errors of 5 mm up to 119 mm occur. The distortion strongly depends on the electromagnetic technology as well on the probe technology used. Thus, for 3D ultrasound-guided applications using electromagnetic tracking technology, the interference of ultrasound probes and electromagnetic sensors have to be checked carefully.

Electricity↗
PubMed2005

Intraoperative assessment of right ventricular volume and function.

OBJECTIVE: Right ventricular function is an important aspect of global cardiac performance which affects patients' outcome after cardiac surgery. Due to its geometrical complexity, the assessment of right ventricular function is still a very difficult task. Aim of this study was to investigate the value of a new technique for intraoperative assessment of right ventricle based on transesophageal 3D-echocardiography, and to compare it to volumetric thermodilution by using a new generation of fast response thermistor pulmonary artery catheters. METHODS: Twenty-five patients with coronary artery disease underwent 68 intraoperative measurements by 3D-echocardiography and thermodilution simultaneously. Following parameters were analysed: right ventricular end-diastolic volume (RVEDV), end-systolic volume (RVESV) and ejection fraction (RVEF). Pulmonary, systemic and central venous pressures were simultaneously recorded. Segmentation of right ventricular volumes were obtained by the 'Coons-Patches' technique, which was implemented into the EchoAnalyzer, a multitask system developed at our institution for three-dimensional functional and structural measurements. RESULTS: Right ventricular volumes obtained by 3D-echocardiography did not show significant correlations to those obtained by thermodilution. Volumetric thermodilution systematically overestimates right ventricular volumes. Significant correlations were found between RVEF measured by 3D-echocardiography and those obtained by thermodilution (r=0. 93; y=0.2+0.80x; SEE=0.03; P<0.01). Bland-Altmann analysis showed that thermodilution systematically underestimates RVEF. The bias for measuring RVEF was +15.6% with a precision of +/-4.3%. The patients were divided into two groups according to left ventricular function. The group of patients with impaired function showed significantly lower right ventricular ejection fraction (44.1+/-4.6 vs. 55.1+/-3.9%; P<0.01). CONCLUSIONS: Three-dimensional echocardiography provides a useful non-invasive tool for intraoperative and serial assessment of right ventricular function. This new technique, which overcomes the limitations of previous methods, may offer key insights into management and outcome of patients with severe impairment of cardiac function.

Aged↗
PubMed2005

The medical imaging interaction toolkit.

Thoroughly designed, open-source toolkits emerge to boost progress in medical imaging. The Insight Toolkit (ITK) provides this for the algorithmic scope of medical imaging, especially for segmentation and registration. But medical imaging algorithms have to be clinically applied to be useful, which additionally requires visualization and interaction. The Visualization Toolkit (VTK) has powerful visualization capabilities, but only low-level support for interaction. In this paper, we present the Medical Imaging Interaction Toolkit (MITK). The goal of MITK is to significantly reduce the effort required to construct specifically tailored, interactive applications for medical image analysis. MITK allows an easy combination of algorithms developed by ITK with visualizations created by VTK and extends these two toolkits with those features, which are outside the scope of both. MITK adds support for complex interactions with multiple states as well as undo-capabilities, a very important prerequisite for convenient user interfaces. Furthermore, MITK facilitates the realization of multiple, different views of the same data (as a multiplanar reconstruction and a 3D rendering) and supports the visualization of 3D+t data, whereas VTK is only designed to create one kind of view of 2D or 3D data. MITK reuses virtually everything from ITK and VTK. Thus, it is not at all a competitor to ITK or VTK, but an extension, which eases the combination of both and adds the features required for interactive, convenient to use medical imaging software. MITK is an open-source project (www.mitk.org).

Algorithms↗
PubMed2004

Regurgitant jet evaluation using three-dimensional echocardiography and magnetic resonance.

BACKGROUND: Three-dimensional assessment of regurgitant jet volume is the prerequisite for stratifying valve insufficiency. However, systematic comparison of three-dimensional methods is lacking. Therefore, we evaluated magnetic resonance imaging and three-dimensional echocardiography experimentally. METHODS: An insufficiency chamber (22 x 18.5 x 27 cm; ostia 10, 16, and 20 mm; regurgitant volumes 2.3 to 25 mL) within experimental circulation (BioMedicus pump, tubes, pulsatile flow 0.2 to 1.9 L/min) was used for three-dimensional echocardiography (HP Sonos 2500) and magnetic resonance imaging (Siemens Magnetom Vision). Doppler flowmeter served as a gold standard. Segmentation used thresholding and surface integration of velocity vectors. Jet volume was evaluated qualitatively by polynom fitting. RESULTS: Jet volume calculated by magnetic resonance (r = 0.99, p < 0.0001) and by echocardiography (r = 0.99, p < 0.0001) correlated identically to the gold standard. Jet volume derived from imaging correlated with each other by r = 0.98 (p < 0.0001). Polynom fits indicated a more paraboloid shape of magnetic resonance jet volume. CONCLUSIONS: Experimentally, three-dimensional echocardiography and magnetic resonance imaging possess identical accuracy for determining regurgitant jet volume. Magnetic resonance imaging seems to provide qualitatively better image data for three-dimensional reconstruction.

Echocardiography, Three-Dimensional↗
PubMed2002

ROPES: a semiautomated segmentation method for accelerated analysis of three-dimensional echocardiographic data.

Echocardiography (cardiac ultrasound) is today the predominant technique for quantitative assessment of cardiac function and valvular heart lesions. Segmentation of cardiac structures is required to determine many important diagnostic parameters. As the heart is a moving organ, reliable information can be obtained only from three-dimensional (3-D) data over time (3-D + time = 4-D). Due to their size, the resulting four-dimensional (4-D) data sets are not reasonably accessible to simple manual segmentation methods. Automatic segmentation often yields unsatisfactory results in a clinical environment, especially for ultrasonic images. We describe a semiautomated segmentation algorithm (ROPES) that is able to greatly reduce the time necessary for user interaction and its application to extract various parameters from 4-D echocardiographic data. After searching for candidate contour points, which have to fulfill a multiscale edge criterion, the candidates are connected by minimizing a cost function to line segments that then are connected to form a closed contour. The contour is automatically checked for plausibility. If necessary, two correction methods that can also be used interactively are applied (fitting of other line segments into the contour and searching for additional candidates with a relaxed criterion). The method is validated using in vivo transesophageal echocardiographic data sets.

Algorithms↗
PubMed2002

Virtual reality in 3D echocardiography: dynamic visualization of atrioventricular annuli surface models and volume rendered Doppler-ultrasound.

Knowledge about annuli shape and blood flow patterns, both optimally assessed by transesophageal 3D Doppler echocardiography, can be used in computer assisted surgical planning of heart valve reconstruction. Moreover, information about the individual shape of the annulus anatomy can guide the design of annular prostheses. The problem is that the annulus cannot be easily differentiated from the valve and the myocardium with standard visualization methods. We have developed a nearly automatic method for annulus segmentation. The algorithm provides the annulus shape in a symbolic description, which can be used for surface visualization. Best results to visualize the blood flow from the Doppler signal and the myocardial morphology are obtained by volume rendering. A hybrid visualization technique combining surface rendering and volume rendering enables to dynamically visualize the surface rendered annulus combined with a volume rendered 3D (plus time) reconstruction of either backscatter (morphology) and Doppler information (in original color coding), or together with backscatter only or Doppler only. Visualization of annuli structures combined with blood flow and general myocardial morphology provides a new tool to analyze heart diseases.

Blood Flow Velocity↗